Tracer study using 13C stable isotope. - (Apr/04/2012 )

So, for my graduate course I need to come up with a mock grant proposal to study a mechanism of the gut microbiota influencing obesity. I chose to look at the effect of the microbiota on the break down of carbohydrates as a mechanism which contributes to obesity (ie in obese people the microbiota is more efficient at breaking down carbohydrates than in lean people, which there is some evidence for). For one experiment I'm proposing to use a stable isotope labelled starch, specifically maize starch which is a resistant starch that is broken down by our gut microbiota. I luckily found a company that actually makes 13C maize starch, so I'm proposing feeding this to obese and lean mice. Here is where I get kind of lost. I don't know if it is possible to measure the amount of the 13C isotope in the mice tissues say after a couple weeks of feeding or the feces? Is this at all possible? Assuming the starch gets broken down into smaller units? I would think that some would be excreted? or absorbed by the host?
Thanks

-Ryan Ho-

It should work just like ordianry C12 works. Your project is definitely feasible. Check out stable isotope analysis and pulse-chase experiments.